A BB92 BB takes any standard crankset (the same as BSA 68 and 73 mm), it's just that with BB92 the bearings are inside the frame when they are outside for 68/73mm BB.
I finally got it, BB92. I'll only need a pressfit BB. Very good. So the Q factor is within a standard range (3,25 tires -> wider chainstays?), no fatsize crank spindles needed?
Once you'll get into the + size you'll just stick to it, trust me. Pick whatever rims width you want but not for such a wrong reason.
Ok, you're right. It's stupid to consider options that will never happen. This bike will be a 29+, basta.
BUT: I couldn't find any 29+ carbon wheelsets with 50mm on aliexpress or alibaba other than the ICAN wheelset for 590EUR with Powerway hubs (ICAN website) or Novatec hubs (ebay), Peter as well only lists the 40mm wheelset. I'm not capable of building wheels myself. Any recommendations?